Femtosecond laser incisions an option for astigmatism after PK

July 1, 2013

A femtosecond laser platform (IntraLase 150 kHz, Abbott Medical Optics) creates low-energy incisions that are safe, effective, accurate and reproducible for treating astigmatism associated with penetrating keratoplasty.

Take-Home

A femtosecond laser platform (IntraLase 150 kHz, Abbott Medical Optics) creates low-energy incisions that are safe, effective, accurate, and reproducible for treating astigmatism associated with penetrating keratoplasty.

(Table courtesy of Eric D. Donnenfeld, MD)

San Francisco-A femtosecond laser platform (IntraLase 150 kHz, Abbott Medical Optics) creates low-energy incisions that are safe, effective, accurate and reproducible for treating astigmatism associated with penetrating keratoplasty (PK).

Erfan Nadji, MD, and senior author, Henry Perry, MD, along with colleagues, conducted a prospective, interventional case series study to evaluate the efficacy and safety of the femtosecond laser platform for treating this patient population. Dr. Nadji highlighted the outcomes in a presentation during the annual meeting of the American Society of Cataract and Refractive Surgery.

The arcuate astigmatic keratotomies that were created with the femtosecond laser are adjustable, unpaired, proportionally targeted at topographic hemi-meridians, and beveled at a 10° angle. Twenty-four patients with visually relevant corneal astigmatism following PK were included in the study.

Incision dynamics

The investigators created one or two relaxing arcuate incisions on the steep corneal hemi-meridians guided by a topographic map. According to Dr. Nadji, two 40° incisions were created for astigmatism <4 D (a total of 80°), two 50° incisions for 4 to 6 D (a total of 100°), and two 60° incisions for >6 D (a total of 120°).

For cases in which the hemi-meridians were different magnitudes, the total degrees of the keratotomies were distributed unevenly, said Dr. Nadji, Nassau University Medical Center, East Meadow, NY.

The incisions were made to a depth of 80% of the thinnest corneal thickness, according to tomographic results. The laser settings were as follows: diameter, 6.5 mm; energy, 1.3 mJ; spot separation, 4 µm; layer separation, 5 µm; and angle of incision, 80°.

Refractive comparisons

Patients were examined on the first postoperative day and month 1 postoperatively. Investigators compared the preoperative and postoperative uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), spherical equivalent (SE), and total amounts of topographic and refractive astigmatism. Dr. Nadji reported using these settings; the arcuate keratotomies remained closed at the conclusion of the laser treatment and moderate effort was needed to open the incisions with a blunt instrument.

The mean preoperative logMAR BCVA of 0.57 ± 0.4008 decreased significantly to 0.18 ± 0.18 postoperatively (p = 0.0045), and the preoperative UCVA of 1.00 ± 0.35 increased significantly to 0.71 ± 0.36 (p = 0.049). The mean preoperative topographic astigmatism decreased from 7.52 ± 2.88 to 4.58 ± 2.69 (p = 0.013). SE did not change significantly from preoperatively to postoperatively. The average surgically induced astigmatism was 4.37 ± 3.31; the average absolute angle of error was 14.07 ± 3.31; and the average index of success was 0.59 ± 0.27, according to Dr. Nadji.

“This was the first prospective study of [this] femtosecond laser system used to treat astigmatism with arcuate keratotomies that are low-energy and thus adjustable, unpaired, proportionally targeted at topographic hemi-meridians, and beveled at an angle of 10°,” Dr. Nadji said. “The advantages of the incisions created with the femtosecond laser are their accuracy and reproducibility. The advantage of low-energy keratotomies is that they can remain closed if a good clinical outcome was achieved.”

Eric D. Donnenfeld, MD

E: ericdonnenfeld@gmail.com

Dr. Donnenfeld did not indicate a financial interest in the subject matter.

Erfan Nadji, MD

Dr. Nadji has no financial interest in the subject matter.

 

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